1. Field of the Invention
The present invention relates to a privacy screen to provide for private viewing of images on a display provided by a color cathode ray tube. The privacy screen of the present invention allows for images on the color cathode ray tube to be visible to an observer directly in front of the tube, but with the images on the color cathode ray tube shielded from observers positioned on either side of the observer in front of the color cathode ray tube.
2. Background of the Prior Art
Various types of display screens are used for transactional purposes. For example, many banking transactions are now carried out using an automatic teller machine (ATM) and with the customer interacting with a terminal including a display screen to perform a banking transaction. During this banking transaction, the display screen may provide images which include information about the customer's account or accounts and the customer, typically, would prefer this information to be retained in confidence and not visible to other customers of the bank.
The customer would normally shield the information on the display screen from any other customers behind the customer performing the financial transaction. However, the information on the display screen would be readily visible to any persons located to either side of the customer performing the financial transaction. It is, therefore, desirable to provide for a means of insuring privacy of the information presented as images on the display screen from persons located to either side of the customer.
The prior art has provided for structures that are used to provide for the above described privacy for black and white or monochrome cathode ray tubes. With these monochrome cathode ray tubes, the lines of information forming the images on the tube are horizontal. The privacy is provided by a light control film, such as a light control film sold by the Industrial Optics division of 3M Company. This 3M light control film (LCF) is a thin plastic film containing closely spaced black microlouvers. The film simulates a thin venetian blind to shield out unwanted ambient light and direct the display light of the CRT tube so that this light is visible only through a particular viewing angle.
The light control film (LCF) is used with the monochrome CRT by having the louvers of the film positioned vertically relative to the horizontal lines of the monochrome CRT. This structure works well in providing privacy and the viewing angle would be dependent on the physical characteristics of the closely spaced microlouvers including the spacing between the louvers, the thickness of the louvers and the depth of the louvers. The light control film (LCF) also has other advantages in enhancing the contrast of the electronic display and can block unwanted external light which would tend to cause reflections and thereby make the display more difficult to read.
Unfortunately, the light control film (LCF) cannot be used with a color CRT in a normal way with the film having the louvers positioned vertically relative to the color CRT. This is because the dot matrix for a color CRT provides for more than horizontal lines. Specifically, a plurality of lines are provided in a color CRT including horizontal lines, vertical lines and angular lines. If a prior art light control film (LCF) is positioned in front of a color CRT, then the interaction of the different lines on the color display with the vertical louvers provide for moire patterns including wave patterns and ring patterns on the display. It can be appreciated that such moire patterns would defeat the visibility of the images on the display and although the prior art light control film might provide for privacy with a color CRT, the privacy would be useless since the images would be effectively lost within the moire patterns.